1. Field of the Invention
The dead front electrical connector comprising the present invention falls into that category of electrical wiring devices known generally to the trade as cord connectors. Connectors of this type may be male or female, and are generally attached to the ends of insulated conductors or cables for use in supplying power to portable machinery, motors, or other electrical equipment or appliances, at locations which may be remote from a permanent electrical outlet.
Connectors of this type are often attached to the associated conductors in situ, and in the circumstances it is important that the connector be adapted for quick and sure attachment to its associated conductor, and in a manner to assure to the maximum extent against loosening of the desired electrical connection of the conductor to the connector during regular use of the device. This is of particular importance considering the fact that the device may be subjected to hard and frequent use in shops, factories, and other commercial establishments, as well as in residential environments.
The connector may be generally classified as being of the type in which the conductor is inserted in one end of a body portion, which thereafter is coupled to a forward portion having male or female contacts, and provided, in the present instance, with a "dead front" for safety purposes.
The strain-relief means of the present invention may have general application to any type of electrical connector in which a conductor is to be engaged within and strain-relieved in the body of a wiring device, whether it be a male or a female cord connector, a cube tap, a cord-mounted switch, or an electrical plug or cap, to state some examples adapted for incorporation of the strain-relief therein. Other examples are electrical connections in a panel or wiring box or appliance housing.
2. Description of the Prior Art
Heretofore, cord connectors of the type referred to have generally possessed one or more of a number of undesirable characteristics.
In some instances, the cord connectors of the prior art have been exceedingly expensive, having a large number of parts which not only are high in cost, considering the cost of the parts themselves, but also, involve excessive expenditure as regards assembly labor.
In other instances, the cord connectors of the present invention have had the undesirable characteristic wherein they can be assembled on the job, or by the ultimate purchaser, only at the cost of an excessive amount of time. In such instances, it has been common to provide a plurality of elongated screws, which must be individually threaded into cooperating openings on one of the connector parts, for the purpose of assembling the cooperating connector part or parts therewith.
In still other instances, the device, when assembled with a conductor, has failed to provide sufficient guarantee that the conductor will be securely locked in place. In some instances, the conductor or power cable has no capability of holding the parts of the connector against accidental disengagement. Rather, the conductor is engaged in one of the connector parts by a means individual to that part. The connection of the connector parts, in the prior art, has then been achieved by means completely separate and distinct from the means employed to engage the cable or conductor. In still other devices, after connection of the connector parts to each other, there is nothing that responds to the act of connecting the parts and the clamping of the cable to automatically lock them together against accidental separation. Locks against accidental separation, if they do exist, in such instances must be a means separate and distinct from, and having no direct cooperation with, the means for coupling the connector body components and the clamping of the cable.
In the prior art, strain relief means has been provided, usable in cord connectors of the type previously described herein as well as in other wiring devices, that have not been possessed of the desired high efficiency as regards gripping of the conductor or cable tightly within the wiring device body. In some instances, a strain relief means is built directly into cooperating, facing portions of the body, and a means of this type is obviously highly efficient, so long as the conductor is of a prescribed exterior diameter and has insulation of a predetermined deformability. In such instances, further, strain-relief is achieved only when the body is connected, and it is necessary to completely disconnect the sections of the body, one from the other, in order to free the conductor. Such prior art devices, though efficient under the predetermined, controlled conditions described, do not allow effective discharge of the strain-relief function of the conductor size is not accurately maintained. Nor do the prior art devices allow adjustment of the strain relief according to the relative deformability of the insulation, that is, the strain relief force exerted against the conductor cannot be increased or reduced, according to the needs of the particular situation as determined by the cable size and the type and relative resistance of the insulation to deformation.